Electrical measuring instb



F. VW. ROLLER.

ELECTRICAL MEASURNG INSTRUMENT.

APPLICM'ION FILED DEC. 15. 1914.

Patented Aug. 12, 1919.

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UNITED sTATns PATENT onirica FRANK W. ROLLER, or EAST ommen, New JERSEY, assrsnon Tc nonnen-:arms

COMPANY, A. CORPORATIQN GF NEW YORK.

.E'LEC'IJJRIQAI MEASURNG INSTRUMENT.

Speeca'con' of Letters Patent.

atented fing. 1 2, 1%;

Application filed December 15 1914. Serial No. 877.232.

To all whom t may concern:

Be it known that I, FRANK YV. Roimnn, a citizen of y the United States, residing at East Orange, in the-county of Essex and State of New Jersey, have' invented certain new 4and useful Improvements in Electrical r.Measuring Instruments, of which the followv simplified forni of construction., a. small number of parts, a high degree of durability, a.- relatively large capacity, a compact construction and convenient, accessibility and have its indications well damped. Other objects and advantages of iny'invention will be understood from the following description.

and accompanying drawings.

Figure 1 isa plan vien7 ofone forni of instrument 'einlbodying my invention, certain parts being broken away and shown in sec# tion for showing the interior construction.

Fig. 2 is a vertical section in the line a--a of Fig. 1, and Fig. 3 is a front elevation of certain of the parts on the line b-b of Fig. 1.

The instrument is provided with a der 1 forming part of the casing and portion 2` which closes one end inder. The opposite end of the cylinder is closed by a glass plate 3.' Secured to the cylinder 1 is a supporting ring or iiange 4 havcylina base ingholes 5 for supporting the instrument against any suitable board or plate such as the dash-board of an automobile. The ring 4 extends over the edge of the glass pla'te 3 tor the purpose of holding the same in place from outward movement, the wire 6 serving to hold the glass plate against the support 4, the wii'e bein;r soldered, or seated in a groove, oi' otherwise secured in place. The base 2 is removably secured to the cylinder 1 by any,v suitable .means such' as the screws 7.

The permanent magnet 8 having poles 9, 9 issupported on tliebaseQby studsor supports 10 located under enlarged port-ions 11 formed on theniagnet. Between the pole pieces is located a hollow cylindrical soft The hollow screw 17 has `which is sup Y lock nuts 23 l of the cyli in dotted lines in Fig.

iron' or steel core 12 viding a goed magnetic conductor between the poles of the magnet and for providing two air gaps between the iron core and the poles. In these air gaps is located a metai cylindrical or bell-sliaped/part 13 of nonmagnetic material, and preferably of. high electrical conductivity, such as copper. The iron cylinder 12 rest-s for the purpose cil proupon one end of a' r hollow supporting cylinder 14e, of non-mag- .netic material, which cylinder has a flange l5 `at its upper portions of the poles 9, 9 of the magnet. Over the lower or inner end of cylinder 1a is fitted a cylindrical cap piece 1S of nonmagnetic material, which engages the lower or inner portions of the pole pieces 9, 9.

a. threaded engagement with the end of and servesl to firmly clamp together' the core '12 and the tivo cylinders 14e, 16 and to also liri'nly secure them to the poles of the perinanent magnet.

The conducting cylinder 13 which serif-es to 'dampen the movement of theinovable element is supported at its outer end upon the sha-ft 18, being clamped in place, as Well as the indicator needle'lt, between the' nuts 20. The shaft is supported atlits' opposite ends in adjustable bearing screws 21, each of orted `in a bridging piece 22, eilig provided for locking the bearing screws 21 in any desiredadjusted position. The outer bridging piece 22 is supported by posts 2a upon the tange 15 or' the cylinder 14; and the inner bridging piece 22 is supported upon' the ange 25 or the cap piece 16 by similar posts 21,. The cylinder 14 is larger in diameter than the distance between the pole pieces 9, 9 and the body portion of the cylinder is cut away on opposite sides so as to tit over the poles, thus centering all of the operative parts.

Near the inner end of the shaft 18 is mounted an armature 26 of soft iron orv ,a zero indica'tion of the instrument, its long'- tudinal axis is parallel to a horizont-al line extending between the pole pieces 'as shown l.

In order to create a deecting field, I provide an exciting or in'agnetizing coil 27 having an iron core 28. This iron core is shown as a flat plate having. its upper end notched end which engages the topv the iron -cylinder 12 lll ill

, Lerares and adapted to slide under the head of a rii'et 529 lixed tothe base fr slot Il() is provided near the opposite end oi' the core .28 and is adajited to receive the. screw Bl ii'hich has threaded engagement with a 'post which latter is fixed to the base The coro 22S is adjustable lmigitudinaliy and sideifise at one end within the coil f2? and is clamped in any desired position by the seinenill. ln order to secure a symmetrical arrangement of the coil, two central wires are led from one terminal, which wires di 'ide and separately iorin turns ol the coil as shown in Fig. i7 the outer ends of the coil being Drought together and connected to the other terminal. ln order to prm'ide room for certain of the parts, the hase 2 has a rectangular depressed central portion as shown in Fig. 2 and ,by full linea and dotted lines in Fig l. The terminals of the instrument are shown as comprising bolts 33, to the l ends 3i' of which are respectively connected the. vterminals 0i" the coil. 37 by a soldered connection or otherwise. rl`he bolts 3? are suitably insulated lfrom the base 2 and held in 'place :thereon by nuts 35. .4

The scale plate '36 is supported upon the magnet S'hy posts 3T ln the. torni ot. instrument disclosed, the cent-ral position ot' the'needle indicates absence oil any current, a deflection to the right indicating flow of current in one direction and a deflection to the left, indicating a flow of current in the opposite direction, this form loe'uigg,r particularly' adapted for use in thebattery circuit in electrical systems for automobiles.

l-Yhen no current fiousthrough the coil of the instrument, the only magnetic flux created and which affects the movable element of the instrument. is that ot' thc permanent magnet S, n'l'iicli gives a strong magnetic field across the air Iaps between the poles and the iron cylinder it), buty also gives a stray field which affects the armature Q6 and tends to hold the same. with its longitudinal airis parallel with, the lines of force existingr between the 1poles l), Sl. lllhen current passes through the coil "i7 oi' the instrument, it tends to set up a magnetic lield substantially at right angles to that created by the permanent magnet, which results in distortion ot the magnetic field aii'ectinfrthi armature 2o and which will vcausevthe armature Q53 to move to a new position sons to place itself in substantial alinement with theresultant. inagnietic field and ,ejive a corret s apparent. that the nrenter thc strength.

-urrent passing through the coil 27 o. instrunuait`r the greater ,will be the cor- 'espoi'idinjj deflection ot the indicating; nel. lle. the maximum deflection oi: the needle 'torni sho-wn beingA rejnesented as 20 ampli in this position the armature 26 has shnted from a horiaontal position indi spoiulinglf deflection oi the indicatingneedle.`

cated in dotted lines 2li in Fie. l to the iuclined position as indicated by the dotted lines 2b in Fig. l. lt is apparent that when current ilons through 1the coil '1T in the opposite direction` the resultara magnetic iield -u'ill canse the 'armature 2li to rotate in a through the coil of the instrument. The slot v or opening`A E() through which the screw 3l passes is also sufficiently wide to permit Sonie siden'ise movement ofi the lower end of the lcore 2S. This sidenise adjustment provides means for adjustment of the zero position oi the needle, the shitting of the end of the core ailecting the distribution of the magnetic lield in the neighborhood of the arn'iature 2G sufficiently for obtaining adjustment for a Zero position.

lt will he noted that in the Jform of construction described7 the armature Q6 subjected to the stray field onlyot the permanent magnet, whereas the cylinder .i3 is subjected directly to the strong magnetic field in the air gaps between the pole pieces of the magnet and the iron core l2, and consequently is subjected to the major portion of the magnetic field created by the permanent magnet.. '.llhe strong lield to which the cylinder i3 is subjected and the high electrical conductivity of the cylinder 13 results in a very stroopr dampening action upon the movable element, by reason of the vstrong eddy currents induced. This action is So effective as to cause the movable elen'lent to be exceedingly steady in its indications under all conditions and even when used on automobiles where it is continually subjected to shocks and jars.

It. is evident that my improved forni of construction leliminates the necessity of a number of delicate parts such as the Inovaloly mounted coil and spring-s for restraining the movable element and likewise by its sirnplicity and rugged construction serves to give durability in use. lt is also compact and readily accessible by removing the base 2 from the easing, all parts being supported from this base. rEhe instrument is also readil y calibrated and gives ahigh degree of accuracy.

Although l have described an instrument as adapted 'particularly for the measuring of a current, it will be understood that my improved construction, may also be utilized in instruments adapted for measurement of voltaire.

lt will also be understood that various modifications in'the form of construction may be made from the particular construction above desclibed without departing l from the scope of the invention.

Having thusdescribed my invention, what I declare as new and 'desire to secure by Letters Patent of the United States is i An electrical'instrument. comprising a perment and passing through said core, a stationary winding, an armature carried by said shaft and affected by the eld of Said magnet and of said winding, and means clamping the poles of said magnet for supporting said core and said shaft.

In testimony whereof I affix my signature in presence of two Witnesses.

FRANK W. ROLLER. 'Witnesses L. K. SAGER, M. D. ISUL. 

